Location-aware profiles in an aerial network

ABSTRACT

Disclosed embodiments may help an aerial vehicle network to provide substantially continuous service in a given geographic area. An example method may be carried out at an aerial vehicle that is at a location associated with the first geographic area in an aerial network that includes a plurality of geographic areas. The balloon may determine that it should update its vehicle-state in accordance with a vehicle-state profile for the first geographic area. Then, in response, the balloon may determine the vehicle-state profile for the first geographic area, which may include one or more state parameters for balloons operating in the first geographic area. The balloon may then operate according to the vehicle-state profile for the first geographic area.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of co-owned U.S. patentapplication Ser. No. 15/013,850, filed Feb. 2, 2016, now pending, whichis a continuation of U.S. patent application Ser. No. 13/485,514, filedon May 31, 2012, which claims priority to U.S. patent application Ser.No. 13/366,100, filed Feb. 3, 2012, all of which are incorporated byreference herein in their entirety and for all purposes.

BACKGROUND

Unless otherwise indicated herein, the materials described in thissection are not prior art to the claims in this application and are notadmitted to be prior art by inclusion in this section.

Computing devices such as personal computers, laptop computers, tabletcomputers, cellular phones, and countless types of Internet-capabledevices are increasingly prevalent in numerous aspects of modern life.As such, the demand for data connectivity via the Internet, cellulardata networks, and other such networks, is growing. However, there aremany areas of the world where data connectivity is still unavailable, orif available, is unreliable and/or costly. Accordingly, additionalnetwork infrastructure is desirable.

SUMMARY

In one aspect, a computer-implemented method involves: (a) at a balloonthat is at a location associated with the first geographic area in aballoon network, wherein the balloon network comprises a plurality ofgeographic areas, determining that a balloon-state of the balloon shouldbe updated in accordance with a balloon-state profile for the firstgeographic area, and (b) in response to determining that theballoon-state should be updated: (i) determining the balloon-stateprofile for the first geographic area, wherein the balloon-state profilecomprises one or more state parameters for balloons operating in thefirst geographic area; and (ii) causing the balloon to operate accordingto the balloon-state profile for the first geographic area.

In another aspect, a non-transitory computer-readable medium may haveprogram instructions stored thereon that are executable by at least oneprocessor. The program instructions include: (a) instructions fordetermining that a balloon should be updated with balloon-stateinformation for a first geographic area in a balloon network, whereinthe balloon is at a location associated with the first geographic area,and wherein the balloon network comprises a plurality of geographicareas; and (b) instructions for, in response to determining that theballoon-state information should be updated: (i) determining aballoon-state profile for the first geographic area, wherein theballoon-state profile comprises one or more state parameters forballoons operating in the second geographic area; and (ii) causing theballoon to operate according to the second balloon-state profile.

In yet another aspect, a computer-implemented method involves: (a) at aballoon that is operable in a balloon network that comprises a pluralityof geographic areas, determining that the balloon is at a locationassociated with the first geographic area in the balloon network; (b)determining a balloon-state profile for the first geographic area,wherein the balloon-state profile comprises one or more state parametersfor balloons operating in the first geographic area; and (c)transmitting a balloon-state signal via a communication channel, whereinthe communication channel is accessible to one or more other balloonsthat are operable in the balloon network, wherein the balloon-statesignal indicates at least a portion of the balloon-state profile for thefirst geographic area.

In a further aspect, a non-transitory computer-readable medium may haveprogram instructions stored thereon that are executable by at least oneprocessor. The program instructions include: (a) instructions fordetermining that a balloon is at a location associated with the firstgeographic area in a balloon network, wherein the balloon networkcomprises a plurality of geographic areas; (b) instructions fordetermining a balloon-state profile for the first geographic area,wherein the balloon-state profile comprises one or more state parametersfor balloons operating in the first geographic area; and (c)instructions for transmitting a balloon-state signal via a communicationchannel, wherein the communication channel is accessible to one or moreother balloons that are operable in the balloon network, wherein theballoon-state signal indicates at least a portion of the balloon-stateprofile for the first geographic area.

These as well as other aspects, advantages, and alternatives, willbecome apparent to those of ordinary skill in the art by reading thefollowing detailed description, with reference where appropriate to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified block diagram illustrating a balloon network,according to an exemplary embodiment.

FIG. 2 is a block diagram illustrating a balloon-network control system,according to an exemplary embodiment.

FIG. 3 shows a high-altitude balloon, according to an exemplaryembodiment.

FIG. 4 is a simplified block diagram illustrating a balloon network thatincludes super-nodes and sub-nodes, according to an exemplaryembodiment.

FIG. 5A is a simplified flow chart illustrating a method, according toan exemplary embodiment.

FIG. 5B is a flow chart illustrating a method, which is a continuationof the method shown in FIG. 5A, according to an exemplary embodiment.

FIG. 6 is a simplified flow chart illustrating a method, according to anexemplary embodiment.

DETAILED DESCRIPTION

Exemplary methods and systems are described herein. It should beunderstood that the word “exemplary” is used herein to mean “serving asan example, instance, or illustration.” Any embodiment or featuredescribed herein as “exemplary” is not necessarily to be construed aspreferred or advantageous over other embodiments or features. Theexemplary embodiments described herein are not meant to be limiting. Itwill be readily understood that certain aspects of the disclosed systemsand methods can be arranged and combined in a wide variety of differentconfigurations, all of which are contemplated herein.

I. Overview

Exemplary embodiments may be implemented in association with a datanetwork that includes a plurality of balloons; for example, a meshnetwork formed by high-altitude balloons deployed in the stratosphere.Since winds in the stratosphere may affect the locations of the balloonsin a differential manner, each balloon in an exemplary network may beconfigured to change its horizontal position by adjusting its verticalposition (i.e., altitude). For example, by adjusting its altitude, aballoon may be able find winds that will carry it horizontally (e.g.,latitudinally and/or longitudinally) to a desired horizontal location.

In an exemplary balloon network, balloons may move latitudinally and/orlongitudinally relative to one another so as to form a desired topology.However, keeping an individual balloon at a specific location may bedifficult due to winds, and possibly for other reasons as well.Accordingly, the desired topology may define a relative framework and/orrules for positioning of balloons relative to one another, such thatballoons can move with respect to the ground, while maintaining thedesired topology. Thus, at a given location on earth, the particularballoon or balloons that provide service may change over time.

In the context of a geographic location's serving balloon or balloonschanging over time, it may be desirable to provide services and featuresthat, from the perspective of the end user, appear to be substantiallythe same as in an access network where access points remain stationary.Accordingly, in an exemplary embodiment, balloons may implementlocation-aware balloon profiling, such that balloon state is tied, atleast in part, to a particular geographic area, rather than being tiedto a particular balloon or balloons. Thus, while balloons may move aboutgeographically, location-specific balloon-state profiles may help toprovide continuity in services, features, and network functionality in agiven geographic area, such that handoffs as balloons move into or outof the geographic area are substantially transparent to the end user.

In particular, location-specific “ghost” balloon-state profiles may bedefined, which each provide balloon-state information that is specificto a particular geographic area. As such, any balloon that moves into aparticular geographic area may configure itself to operate according tothe area's balloon-state profile for as long as it remains in the area.

Further, location-specific balloon-profiles may be shared betweenballoons. For instance, in some embodiments, balloon-state informationfor a particular geographic area may be handed off between balloons. Asa specific example, a balloon that enters or is about to enter ageographic area may acquire the balloon-state profile for the geographicarea from a balloon or balloons already located in the geographic area(or possibly a balloon or balloons that have just left the area).Further, in some cases, a balloon may acquire some or all of theballoon-state profile for a geographic area from a ground-based station.

A location-specific balloon-state profile may specify various types ofballoon-state information for balloons that operate in its correspondinggeographic area. In some cases, balloon-state information for a givengeographic area may include configuration information and/or operatingparameters for balloons that operate in the area. For example, alocation-specific balloon-state profile may specify a communicationprotocol or protocols to be used by balloons operating in a particulargeographic area. As another example, a location-specific balloon-stateprofile could specify a power-usage profile to be used by balloonsoperating in a particular geographic area (e.g., whether the balloon canshould use more or less power than typical while located in the area).Other examples are possible as well.

Further, balloon-state information for a geographic area could specifyoperating parameters such that balloons that are located in thegeographic area will operate in accordance with legal requirementsestablished by the governing body of the country in which the geographicarea is located. Accordingly, balloons could adapt their operation tovarying legal requirements of differently-governed areas as, e.g., theymove from one country, state, or city to another (and/or to an areawhere international law applies).

Further, balloon-state information for a given geographic area mayinclude or indicate certain data that should be cached in a certainregion. For example, a location-specific balloon-state profile for agiven geographic area might specify that a balloon should cache commonweb pages in a certain language, which is spoken in the given geographicarea. Further, a balloon could acquire the specified data for its cachein a typical manner (e.g., by accessing a URL for the webpage directlyand then storing the webpage), or by requesting and/or receiving thespecified data from nearby balloons.

It should be understood that the above examples of balloon-stateinformation, which may be provided by a balloon-state profile, areprovided for illustrative purposes, and should not be construed aslimiting. As such, a balloon-state profile may additionally oralternatively include other types of balloon-state information, withoutdeparting from the scope of the invention.

Note that the geographic areas, to which balloon-state profiles areassigned, may be defined independently from the coverage reach of theballoons. In other words, the geographic areas may be defined in amanner that is not dependent on the individual coverage areas served byballoons in the balloon network. For instance, in the above examplewhere balloon-state profiles are such that balloons located in ageographic area will operate in accordance with legal requirements inwhatever geographic area they move into, geographic areas may be definedbased on borders established by governing bodies (e.g., borders betweencountries, states, cities, etc.).

Further, in some embodiments, geographic areas may be defined aroundcertain operating requirements for certain areas. For instance,geographic areas may be defined for areas having certain bandwidthrequirements (e.g., where demand for bandwidth is higher or lower thanis typical in the balloon network). For example, a geographic area couldbe defined around a stadium or an arena where sporting events andconcerts take place, so as to help satisfy higher demand for bandwidththat is typically associated with such events. Other examples arepossible.

Yet further, geographic areas may be defined dynamically based onchanging operating requirements in different areas served by a balloonnetwork. For example, if a bandwidth demand in area is observed toincrease significantly, then the geographic area in which the demandincrease occurred, and a corresponding balloon-state profile for thearea, may be dynamically defined.

As a specific example, a stadium that is located in a suburban area maybe located within a larger geographic area, which includes a number ofsuburbs. However, when there is an event at the stadium, the balloonnetwork may detect a spike in bandwidth demand in the localized area inand around the stadium (e.g., an increase over historical norms in thearea that lasts at least an hour), and dynamically define aballoon-state profile for the smaller geographic area in and around thestadium (while removing this smaller geographic area from the largergeographic area for the suburbs). Later, when the event ends and thedemand decreases, the balloon network may detect the decreased demand,and re-define the geographic areas such that the stadium is again partof the larger geographic area for the suburbs. Other specific examplesare also possible.

As another example, geographic areas may be defined based on designconsiderations. For instance, geographic areas may be defined fordifferent areas according to differing power requirements of end usersin the areas, differing interference concerns for RF and/or opticalsignals in the areas, and/or differing types of service desired by endusers in the areas, among other possibilities.

In a further aspect, balloons could also maintain location-aware cachesof user-data, which each balloon updates according to the respectivegeographic area in which it is located. As such, balloons that updatetheir state according to location-specific balloon-state profiles mayalso update their respective location-aware caches as they move in andout of the defined geographic areas, such that whichever balloon orballoons are in a given geographic area can provide the same or asimilar cache of user-data, while located in the given geographic area.Thus, while balloons might move between geographic areas, users in agiven geographic area may be provided with caching functionality thatreplicates, or at least comes close to replicating, the cachingfunctions of a fixed access point.

Further, location-specific balloon-profiles may be assigned to fixedgeographic areas, which are defined by specific geographic coordinates,such as GPS coordinates, for example. However, a location-specificballoon-profile could also be assigned to a moving geographic area. Amoving geographic area may be defined by, e.g., a moving object orperson. For example, a moving geographic area could be defined around avehicle capable of changing its location (e.g., cars, trains, cruiseships, etc.). As another example, a moving geographic area could bedefined around a certain person or group of people, such that there iscontinuity in the service provided to the person or group as they moveabout geographically.

II. Exemplary Balloon Networks

An exemplary embodiment may be implemented in association with varioustypes of balloon networks. For instance, in an exemplary balloonnetwork, the balloons may communicate with one another using free-spaceoptical communications. As an example, the balloons may be configuredfor optical communications using ultra-bright LEDs (which are alsoreferred to as “high-power” or “high-output” LEDs). In some instances,lasers could be used instead of or in addition to LEDs, althoughregulations for laser communications may restrict laser usage. Inaddition, the balloons may communicate with ground-based station(s)using radio-frequency (RF) communications.

In some embodiments, a high-altitude-balloon network may be homogenous.That is, the balloons in a high-altitude-balloon network could besubstantially similar to each other in one or more ways. Morespecifically, in a homogenous high-altitude-balloon network, eachballoon is configured to communicate with one or more other balloons viafree-space optical links. Further, some or all of the balloons in such anetwork may additionally be configured to communicate with ground-basedstation(s) using RF communications. Thus, in some embodiments, theballoons may be homogenous in so far as each balloon is configured forfree-space optical communication with other balloons, but heterogeneouswith regard to RF communications with ground-based stations.

In other embodiments, a high-altitude-balloon network may beheterogeneous, and thus may include two or more different types ofballoons (i.e., two or more types of balloons that function insubstantially different ways). For example, some balloons in aheterogeneous network may be configured as super-nodes, while otherballoons may be configured as sub-nodes. It is also possible that someballoons in a heterogeneous network may be configured to function asboth a super-node and a sub-node. Such balloons may function as either asuper-node or a sub-node at a particular time, or, alternatively, act asboth simultaneously depending on the context. For instance, an exampleballoon could aggregate search requests of a first type to transmit to aground-based station. The example balloon could also send searchrequests of a second type to another balloon, which could act as asuper-node in that context. Further, some balloons, which may besuper-nodes in an exemplary embodiment, can be configured to communicatevia optical links with ground-based stations and/or satellites.

In an exemplary configuration, the super-node balloons may be configuredto communicate with nearby super-node balloons via free-space opticallinks. However, the sub-node balloons may not be configured forfree-space optical communication, and may instead be configured for someother type of communication, such as RF communications. In that case, asuper-node may be further configured to communicate with sub-nodes usingRF communications. Thus, the sub-nodes may relay communications betweenthe super-nodes and one or more ground-based stations using RFcommunications. In this way, the super-nodes may collectively functionas backhaul for the balloon network, while the sub-nodes function torelay communications from the super-nodes to ground-based stations.

FIG. 1 is a simplified block diagram illustrating a balloon network 100,according to an exemplary embodiment. As shown, balloon network 100includes balloons 102A to 102F, which are configured to communicate withone another via free-space optical links 104. Configured as such,balloons 102A to 102F may collectively function as a mesh network forpacket-data communications. Further, at least some of balloons 102A and102B may be configured for RF communications with ground-based stations106 via respective RF links 108. Yet further, some balloons, such asballoon 102F, may be configured to communicate via optical link 110 withground-based station 112.

In an exemplary embodiment, balloons 102A to 102F are high-altitudeballoons, which are deployed in the stratosphere. At moderate latitudes,the stratosphere includes altitudes between approximately 10 kilometers(km) and 50 km altitude above the surface. At the poles, thestratosphere starts at an altitude of approximately 8 km. In anexemplary embodiment, high-altitude balloons may be generally configuredto operate in an altitude range within the stratosphere that hasrelatively low wind-speeds (e.g., between 5 and 20 miles per hour(mph)).

More specifically, in a high-altitude-balloon network, balloons 102A to102F may generally be configured to operate at altitudes between 18 kmand 25 km (although other altitudes are possible). This altitude rangemay be advantageous for several reasons. In particular, this layer ofthe stratosphere generally has relatively low wind speeds (e.g., windsbetween 5 and 20 mph) and relatively little turbulence. Further, whilethe winds between 18 km and 25 km may vary with latitude and by season,the variations can be modeled in a reasonably accurate manner.Additionally, altitudes above 18 km are typically above the maximumflight level designated for commercial air traffic. Therefore,interference with commercial flights is not a concern when balloons aredeployed between 18 km and 25 km.

To transmit data to another balloon, a given balloon 102A to 102F may beconfigured to transmit an optical signal via an optical link 104. In anexemplary embodiment, a given balloon 102A to 102F may use one or morehigh-power light-emitting diodes (LEDs) to transmit an optical signal.Alternatively, some or all of balloons 102A to 102F may include lasersystems for free-space optical communications over optical links 104.Other types of free-space optical communication are possible. Further,in order to receive an optical signal from another balloon via anoptical link 104, a given balloon 102A to 102F may include one or moreoptical receivers. Additional details of exemplary balloons arediscussed in greater detail below, with reference to FIG. 3.

In a further aspect, balloons 102A to 102F may utilize one or more ofvarious different RF air-interface protocols for communication withground-based stations 106 via respective RF links 108. For instance,some or all of balloons 102A to 102F may be configured to communicatewith ground-based stations 106 using protocols described in IEEE 802.11(including any of the IEEE 802.11 revisions), various cellular protocolssuch as GSM, CDMA, UMTS, EV-DO, WiMAX, and/or LTE, and/or one or morepropriety protocols developed for balloon-ground RF communication, amongother possibilities.

In a further aspect, there may scenarios where RF links 108 do notprovide a desired link capacity for balloon-ground communications. Forinstance, increased capacity may be desirable to provide backhaul linksfrom a ground-based gateway, and in other scenarios as well.Accordingly, an exemplary network may also include downlink balloons,which provide a high-capacity air-ground link.

For example, in balloon network 100, balloon 102F is configured as adownlink balloon. Like other balloons in an exemplary network, adownlink balloon 102F may be operable for optical communication withother balloons via optical links 104. However, a downlink balloon 102Fmay also be configured for free-space optical communication with aground-based station 112 via an optical link 110. Optical link 110 maytherefore serve as a high-capacity link (as compared to an RF link 108)between the balloon network 100 and a ground-based station 108.

Note that in some implementations, a downlink balloon 102F mayadditionally be operable for RF communication with ground-based stations106. In other cases, a downlink balloon 102F may only use an opticallink for balloon-to-ground communications. Further, while thearrangement shown in FIG. 1 includes just one downlink balloon 102F, anexemplary balloon network can also include multiple downlink balloons.On the other hand, a balloon network can also be implemented without anydownlink balloons.

In other implementations, a downlink balloon may be equipped with aspecialized, high-bandwidth RF communication system forballoon-to-ground communications, instead of, or in addition to, afree-space optical communication system. The high-bandwidth RFcommunication system may take the form of an ultra-wideband system,which may provide an RF link with substantially the same capacity as oneof the optical links 104. Other forms are also possible.

Ground-based stations, such as ground-based stations 106 and/or 108, maytake various forms. Generally, a ground-based station may includecomponents such as transceivers, transmitters, and/or receivers forcommunication via RF links and/or optical links with a balloon network.Further, a ground-based station may use various air-interface protocolsin order to communicate with a balloon 102A to 102F over an RF link. Assuch, a ground-based station 106 may be configured as an access pointvia which various devices can connect to balloon network 100.Ground-based stations 106 may have other configurations and/or serveother purposes without departing from the scope of the invention.

In a further aspect, some or all balloons 102A to 102F could beconfigured to establish a communication link with space-based satellitesin addition to, or as an alternative to, a ground-based communicationlink. In some embodiments, a balloon may communicate with a satellitevia an optical link. However, other types of satellite communicationsare also possible.

Further, some ground-based stations, such as ground-based station 108,may be configured as gateways between balloon network 100 and one ormore other networks. Such a ground-based station 108 may thus serve asan interface between the balloon network and the Internet, a cellularservice provider's network, and/or other types of networks. Variationson this configuration and other configurations of a ground-based station108 are also possible.

A. Mesh-Network Functionality

As noted, balloons 102A to 102F may collectively function as a meshnetwork. More specifically, since balloons 102A to 102F may communicatewith one another using free-space optical links, the balloons maycollectively function as a free-space optical mesh network.

In a mesh-network configuration, each balloon 102A to 102F may functionas a node of the mesh network, which is operable to receive datadirected to it and to route data to other balloons. As such, data may berouted from a source balloon to a destination balloon by determining anappropriate sequence of optical links between the source balloon and thedestination balloon. These optical links may be collectively referred toas a “lightpath” for the connection between the source and destinationballoons. Further, each of the optical links may be referred to as a“hop” on the lightpath.

To operate as a mesh network, balloons 102A to 102F may employ variousrouting techniques and self-healing algorithms. In some embodiments, aballoon network 100 may employ adaptive or dynamic routing, where alightpath between a source and destination balloon is determined andset-up when the connection is needed, and released at a later time.Further, when adaptive routing is used, the lightpath may be determineddynamically depending upon the current state, past state, and/orpredicted state of the balloon network.

In addition, the network topology may change as the balloons 102A to102F move relative to one another and/or relative to the ground.Accordingly, an exemplary balloon network 100 may apply a mesh protocolto update the state of the network as the topology of the networkchanges. For example, to address the mobility of the balloons 102A to102F, balloon network 100 may employ and/or adapt various techniquesthat are employed in mobile ad hoc networks (MANETs). Other examples arepossible as well.

In some implementations, a balloon network 100 may be configured as atransparent mesh network. More specifically, in a transparent balloonnetwork, the balloons may include components for physical switching thatis entirely optical, without any electrical components involved in thephysical routing of optical signals. Thus, in a transparentconfiguration with optical switching, signals travel through a multi-hoplightpath that is entirely optical.

In other implementations, the balloon network 100 may implement afree-space optical mesh network that is opaque. In an opaqueconfiguration, some or all balloons 102A to 102F may implementoptical-electrical-optical (OEO) switching. For example, some or allballoons may include optical cross-connects (OXCs) for OEO conversion ofoptical signals. Other opaque configurations are also possible.

In a further aspect, balloons in an exemplary balloon network 100 mayimplement wavelength division multiplexing (WDM), which may help toincrease link capacity. When WDM is implemented with transparentswitching, physical lightpaths through the balloon network may besubject to the “wavelength continuity constraint.” More specifically,because the switching in a transparent network is entirely optical, itmay be necessary to assign the same wavelength for all optical links ona given lightpath.

An opaque configuration, on the other hand, may avoid the wavelengthcontinuity constraint. In particular, balloons in an opaque balloonnetwork may include the OEO switching systems operable for wavelengthconversion. As a result, balloons can convert the wavelength of anoptical signal at each hop along a lightpath.

Further, various routing algorithms may be employed in an opaqueconfiguration. For example, to determine a primary lightpath and/or oneor more diverse backup lightpaths for a given connection, exemplaryballoons may apply or consider shortest-path routing techniques such asDijkstra's algorithm and k-shortest path, and/or edge and node-diverseor disjoint routing such as Suurballe's algorithm, among others.Additionally or alternatively, techniques for maintaining a particularquality of service (QoS) may be employed when determining a lightpath.Other techniques are also possible.

B. Station-Keeping Functionality

In an exemplary embodiment, a balloon network 100 may implementstation-keeping functions to help provide a desired network topology.For example, station-keeping may involve each balloon 102A to 102Fmaintaining and/or moving into a certain position relative to one ormore other balloons in the network (and possibly in a certain positionrelative to the ground). As part of this process, each balloon 102A to102F may implement station-keeping functions to determine its desiredpositioning within the desired topology, and if necessary, to determinehow to move to the desired position.

The desired topology may vary depending upon the particularimplementation. In some cases, balloons may implement station-keeping toprovide a substantially uniform topology. In such cases, a given balloon102A to 102F may implement station-keeping functions to position itselfat substantially the same distance (or within a certain range ofdistances) from adjacent balloons in the balloon network 100.

In other cases, a balloon network 100 may have a non-uniform topology.For instance, exemplary embodiments may involve topologies whereballoons are distributed more or less densely in certain areas, forvarious reasons. As an example, to help meet the higher bandwidthdemands that are typical in urban areas, balloons may be clustered moredensely over urban areas. For similar reasons, the distribution ofballoons may be denser over land than over large bodies of water. Manyother examples of non-uniform topologies are possible.

In a further aspect, the topology of an exemplary balloon network may beadaptable. In particular, station-keeping functionality of exemplaryballoons may allow the balloons to adjust their respective positioningin accordance with a change in the desired topology of the network. Forexample, one or more balloons could move to new positions to increase ordecrease the density of balloons in a given area. Other examples arepossible.

In some embodiments, a balloon network 100 may employ an energy functionto determine if and/or how balloons should move to provide a desiredtopology. In particular, the state of a given balloon and the states ofsome or all nearby balloons may be input to an energy function. Theenergy function may apply the current states of the given balloon andthe nearby balloons to a desired network state (e.g., a statecorresponding to the desired topology). A vector indicating a desiredmovement of the given balloon may then be determined by determining thegradient of the energy function. The given balloon may then determineappropriate actions to take in order to effectuate the desired movement.For example, a balloon may determine an altitude adjustment oradjustments such that winds will move the balloon in the desired manner.

C. Control of Balloons in a Balloon Network

In some embodiments, mesh networking and/or station-keeping functionsmay be centralized. For example, FIG. 2 is a block diagram illustratinga balloon-network control system, according to an exemplary embodiment.In particular, FIG. 2 shows a distributed control system, which includesa central control system 200 and a number of regional control-systems202A to 202B. Such a control system may be configured to coordinatecertain functionality for balloon network 204, and as such, may beconfigured to control and/or coordinate certain functions for balloons206A to 206I.

In the illustrated embodiment, central control system 200 may beconfigured to communicate with balloons 206A to 206I via a number ofregional control systems 202A to 202C. These regional control systems202A to 202C may be configured to receive communications and/oraggregate data from balloons in the respective geographic areas thatthey cover, and to relay the communications and/or data to centralcontrol system 200. Further, regional control systems 202A to 202C maybe configured to route communications from central control system 200 tothe balloons in their respective geographic areas. For instance, asshown in FIG. 2, regional control system 202A may relay communicationsand/or data between balloons 206A to 206C and central control system200, regional control system 202B may relay communications and/or databetween balloons 206D to 206F and central control system 200, andregional control system 202C may relay communications and/or databetween balloons 206G to 206I and central control system 200.

In order to facilitate communications between the central control system200 and balloons 206A to 206I, certain balloons may be configured asdownlink balloons, which are operable to communicate with regionalcontrol systems 202A to 202C. Accordingly, each regional control system202A to 202C may be configured to communicate with the downlink balloonor balloons in the respective geographic area it covers. For example, inthe illustrated embodiment, balloons 204A, 204D, and 204H are configuredas downlink balloons. As such, regional control systems 202A to 202C mayrespectively communicate with balloons 204A, 204D, and 204H via opticallinks 206, 208, and 210, respectively.

In the illustrated configuration, only some of balloons 206A to 206I areconfigured as downlink balloons. The balloons 206A, 206F, and 206I thatare configured as downlink balloons may relay communications fromcentral control system 200 to other balloons in the balloon network,such as balloons 206B-E and 206G-H. However, it should be understoodthat it in some implementations, it is possible that all balloons mayfunction as downlink balloons. Further, while FIG. 2 shows multipleballoons configured as downlink balloons, it is also possible for aballoon network to include only one downlink balloon, or possibly evenno downlink balloons.

Note that a regional control system 202A to 202B may in fact just be aparticular type of ground-based station that is configured tocommunicate with downlink balloons (e.g., such as ground-based station112 of FIG. 1). Thus, while not shown in FIG. 2, a control system may beimplemented in conjunction with other types of ground-based stations(e.g., access points, gateways, etc.).

In a centralized control arrangement, such as that shown in FIG. 2, thecentral control system 200 (and possibly regional control systems 202Ato 202C as well) may coordinate certain mesh-networking functions forballoon network 204. For example, balloons 206A to 206I may send thecentral control system 200 certain state information, which the centralcontrol system 200 may utilize to determine the state of balloon network204. The state information from a given balloon may include locationdata, optical-link information (e.g., the identity of other balloonswith which the balloon has established an optical link, the bandwidth ofthe link, wavelength usage and/or availability on a link, etc.), winddata collected by the balloon, and/or other types of information.Accordingly, the central control system 200 may aggregate stateinformation from some or all of the balloons 206A to 206I in order todetermine an overall state of the network.

The overall state of the network may then be used to coordinate and/orfacilitate certain mesh-networking functions such as determininglightpaths for connections. For example, the central control system 200may determine a current topology based on the aggregate stateinformation from some or all of the balloons 206A to 206I. The topologymay provide a picture of the current optical links that are available inballoon network and/or the wavelength availability on the links. Thistopology may then be sent to some or all of the balloons so that arouting technique may be employed to select appropriate lightpaths (andpossibly backup lightpaths) for communications through the balloonnetwork 204.

In a further aspect, the central control system 200 (and possiblyregional control systems 202A to 202C as well) may also coordinatecertain station-keeping functions for balloon network 204. For example,the central control system 200 may input state information that isreceived from balloons 206A to 206I to an energy function, which mayeffectively compare the current topology of the network to a desiredtopology, and provide a vector indicating a direction of movement (ifany) for each balloon, such that the balloons can move towards thedesired topology. Further, the central control system 200 may usealtitudinal wind data to determine respective altitude adjustments thatmay be initiated to achieve the movement towards the desired topology.The central control system 200 may provide and/or support otherstation-keeping functions as well.

FIG. 2 shows a distributed arrangement that provides centralizedcontrol, with regional control systems 202A to 202C coordinatingcommunications between a central control system 200 and a balloonnetwork 204. Such an arrangement may be useful to provide centralizedcontrol for a balloon network that covers a large geographic area. Insome embodiments, a distributed arrangement may even support a globalballoon network that provides coverage everywhere on earth. Of course, adistributed-control arrangement may be useful in other scenarios aswell.

Further, it should be understood that other control-system arrangementsare also possible. For instance, some implementations may involve acentralized control system with additional layers (e.g., sub-regionsystems within the regional control systems, and so on). Alternatively,control functions may be provided by a single, centralized, controlsystem, which communicates directly with one or more downlink balloons.

In some embodiments, control and coordination of a balloon network maybe shared by a ground-based control system and a balloon network tovarying degrees, depending upon the implementation. In fact, in someembodiments, there may be no ground-based control systems. In such anembodiment, all network control and coordination functions may beimplemented by the balloon network itself. For example, certain balloonsmay be configured to provide the same or similar functions as centralcontrol system 200 and/or regional control systems 202A to 202C. Otherexamples are also possible.

Furthermore, control and/or coordination of a balloon network may bede-centralized. For example, each balloon may relay state informationto, and receive state information from, some or all nearby balloons.Further, each balloon may relay state information that it receives froma nearby balloon to some or all nearby balloons. When all balloons doso, each balloon may be able to individually determine the state of thenetwork. Alternatively, certain balloons may be designated to aggregatestate information for a given portion of the network. These balloons maythen coordinate with one another to determine the overall state of thenetwork.

Further, in some aspects, control of a balloon network may be partiallyor entirely localized, such that it is not dependent on the overallstate of the network. For example, individual balloons may implementstation-keeping functions that only consider nearby balloons. Inparticular, each balloon may implement an energy function that takesinto account its own state and the states of nearby balloons. The energyfunction may be used to maintain and/or move to a desired position withrespect to the nearby balloons, without necessarily considering thedesired topology of the network as a whole. However, when each balloonimplements such an energy function for station-keeping, the balloonnetwork as a whole may maintain and/or move towards the desiredtopology.

As an example, each balloon A may receive distance information d₁ tod_(k) with respect to each of its k closest neighbors. Each balloon Amay treat the distance to each of the k balloons as a virtual springwith vector representing a force direction from the first nearestneighbor balloon i toward balloon A and with force magnitudeproportional to d_(i). The balloon A may sum each of the k vectors andthe summed vector is the vector of desired movement for balloon A.Balloon A may attempt to achieve the desired movement by controlling itsaltitude.

Alternatively, this process could assign the force magnitude of each ofthese virtual forces equal to d_(i)×d_(i), for instance. Otheralgorithms for assigning force magnitudes for respective balloons in amesh network are possible.

In another embodiment, a similar process could be carried out for eachof the k balloons and each balloon could transmit its planned movementvector to its local neighbors. Further rounds of refinement to eachballoon's planned movement vector can be made based on the correspondingplanned movement vectors of its neighbors. It will be evident to thoseskilled in the art that other algorithms could be implemented in aballoon network in an effort to maintain a set of balloon spacingsand/or a specific network capacity level over a given geographiclocation.

D. Defined Geographic Areas within a Balloon Network

In a further aspect, which is illustrated by FIG. 2, a balloon networkmay serve a coverage area that is subdivided into a number of definedgeographic areas 220 to 240. Further, while FIG. 2 illustrates threedefined geographic areas 220 to 240, more or less geographic areas maybe defined, without departing from the scope of the invention. Yetfurther, while geographic areas 220 to 240 are shown as distinctcoverage areas that do not overlap, it is possible that two or moregeographic areas may be defined so as to overlap (at least partially).

In an exemplary embodiment, each balloon 206A to 206I may operateaccording to the balloon-state profile of the respective geographic area220 to 240 in which the balloon is located at a given point in time. Forexample, in the illustrated state of balloon network 204, balloons 206Ato 206C may each set their respective balloon state and operateaccording to the balloon-state profile for geographic area 220, balloons206D to 206F may each set their respective balloon state and operateaccording to the balloon-state profile for geographic area 230, andballoons 206G to 206I may each set their respective balloon state andoperate according to the balloon-state profile for geographic area 240.

Further, when a given balloon 206A to 206I moves from one geographicarea to another, the balloon may update its balloon-state accordingly.For instance, if balloon 206C were to move from its location shown inFIG. 2, in geographic area 220, to geographic area 230, balloon 206C mayupdate its balloon-state according to the balloon-state profile forgeographic area 230. In some cases, this may involve balloon 306Cupdating certain settings and/or certain operational parameters, whichwere previously set according to the balloon-state profile forgeographic area 220, as indicated by the balloon-profile for geographicarea 230.

Further, a balloon 206A to 206I could maintain and update alocation-aware cache and/or other data according to the geographic area220 to 240 in which it is located at a given point in time (or ageographic area that the balloon anticipates being located in). Forexample, the balloon-state profile for a given geographic area 220 to240 may indicate that a balloon should acquire, store, and/or providecertain data while operating in the respective geographic area. As aspecific example, in the illustrated state of balloon network 204,balloons 206A to 206C may each store user-data that is associatedgeographic area 220 and/or data this is identified by the balloon-stateprofile for geographic area 220, balloons 206D to 206F may each storeuser-data that is associated geographic area 230 and/or data this isidentified by the balloon-state profile for geographic area 230, andballoons 206G to 206I may each store user-data that is associatedgeographic area 240 and/or data this is identified by the balloon-stateprofile for geographic area 240. Other examples are also possible.

In some cases, such as the example illustrated in FIG. 2, the coveragearea of balloon network may include defined border areas, which separatethe defined geographic areas. In the illustrated embodiment, geographicareas 220 and 230 are separated by border area 222, while geographicareas 230 and 240 are separated by border area 232. Note that a borderarea may also be treated as an area where two or more coverage areasoverlap, rather than a distinct area that separates two adjacentcoverage areas. For instance, border area 222 may be created by defininggeographic areas 220 and 230 such that these geographic areas overlap inborder area 222.

In some embodiments, a balloon 206A to 206I may update (or begin toupdate) its balloon-state when it moves into a border area 222 or 232.In such an embodiment, a border area in a given geographic area may beassociated with the adjacent geographic areas that it separates.Accordingly, when a balloon moves into a border area, it may update orprepare to update its balloon-state according to the balloon-stateprofile for the geographic area or geographic areas associated with theborder area, which the balloon expects or is likely to move into. To doso, the balloon may update or prepare to update operational parametersaccording to the balloon-state profile for the geographic area intowhich it expects to move, and/or may store data identified by theballoon-state profile for the geographic area into which it expects tomove.

For example, a balloon 206C may detect that it has moved from thelocation illustrated in FIG. 2 (with geographic area 220) to a locationwithin border area 222, and responsively prepare to update itsballoon-state and/or update its location-aware cache. Presumably,balloon 206C will have previously updated its balloon-state according tothe balloon-state profile for geographic area 220, and/or will havestored data identified by the balloon-state profile for the geographicarea 220 and/or user-data that is otherwise associated with geographicarea 220 (e.g., by storing such data in a location-aware cache).Accordingly, when balloon 206C moves into border area 222, it mayresponsively prepare to update its balloon-state by determining theballoon-state profile for geographic area 230. Further, balloon 206C maybegin acquiring, locating, and/or storing data that the balloon-stateprofile for geographic area 230 indicates should be provided while theballoon 206C is located in geographic area 230. Additionally oralternatively, when balloon 206C moves into border area 222, it maybegin storing user-data associated with the adjacent geographic area 230in its location-aware cache.

In a further aspect, a balloon may keep previously-stored data in itslocation-aware cache while it is located in a border area. Suchpreviously-stored data may include, but is not limited to: (a) user-datathat is associated with the geographic area in which it is currentlyand/or was previously located in, and/or (b) data that is identified bythe balloon-state profile for the geographic area in which it iscurrently and/or was previously located in. For example, in the abovescenario, if balloon 206C moves into border area 222, it may keep someor all data that is associated with geographic area 220 in itslocation-aware cache, while at the same time acquiring, locating, and/orstoring data that is associated with geographic area 230.

Further, after a balloon 206A to 206I moves into a border area 222 or232, the balloon may wait until it moves out of the border area, and isfully within one of the adjacent coverage areas, before the balloonactually updates its balloon-state and/or deletes data that isassociated with a geographic area in which the balloon was previouslylocated. For example, while balloon 206C is located in border area 222it may have requested and received the balloon-state profile forgeographic area 230. Then, if balloon 206C does in fact move intogeographic area 230, it may then proceed to update its balloon-stateaccording to the balloon-state profile for geographic area 230. Further,if and when balloon 206C moves into geographic area 230, it may alsoremove (or begin deleting data that is associated with geographic area220.

On the other hand, if balloon 206C does not end up moving intogeographic area 230, and moves into or remains within geographic area220 after moving out of border area 222, then balloon 206C may refrainfrom updating its balloon state. In this scenario, balloon 206C couldalternatively update its balloon-state according to the balloon-stateprofile for geographic area 220 (e.g., if the balloon-state profile forgeographic area 220 has changed since balloon 206C last updated itsballoon-state). Additionally or alternatively, if balloon 206C movesinto or remains within geographic area 220 after moving out of borderarea 222, balloon 206C may responsively remove (or begin removing) datathat associated geographic area 230, which it may have stored inanticipation of possibly moving into geographic area 230.

Note that while the border areas 222 and 232 that are illustrated inFIG. 2 can be described and/or defined as areas that separate and/or atleast partially define geographic areas 220 to 240, geographic areas maybe defined without defining border areas. Further, border areas canalternatively be described and/or defined as areas where two or moregeographic areas overlap. As yet another alternative, there may be noborder areas whatsoever (either defined specifically, as areas thatseparate GAs, or as a result of overlapping geographic areas).

In a further aspect, the geographic areas (and border areas, if any) maybe defined so as to create a substantially contiguous coverage area. Forinstance, in the illustrated balloon network 204, geographic areas 220to 240 and border areas 222 to 232 subdivide a substantially contiguouscoverage area. However, it should be understood that the coverage of aballoon network may also extend to locations that are not part of anydefined geographic area or border area, without departing from the scopeof the invention.

To determine and/or update its balloon-state, a given balloon 206A to206I may send a profile-update request to one or more of the otherballoons in balloon network 204. The profile-update request may indicatea current location of the requesting balloon (such that a receivingballoon can determine which geographic area the request is for), and/ormay specifically identify the geographic area for which a cache updateis being requested (e.g., by including an identification number ofanother unique identifier for the GA). A balloon that receives aprofile-update request from another balloon, and has already learnedsome or all of the balloon-state profile for the identified coveragearea, may respond by sending some or all of the balloon-state profilefor the identified coverage area to the requesting balloon.

In some implementations, a balloon 206A to 206I may specifically sendprofile-update requests to another balloon or balloons that are believedto be located a geographic area for which a balloon-state profile isdesired and/or that are believed to be capable of providing some or allof the desired balloon-state profile. In such an embodiment, a balloonthat receives a profile-update request may assume that it is currentlyoperating according to the desired balloon-state profile. In such anembodiment, the requesting balloon may not include an indication of itslocation, or an indication of the geographic area for which user-data isdesired, in a profile-update request. Further, the receiving balloon mayrespond to the request by automatically sending a balloon-state signalthat indicates and/or provides the balloon-state profile according towhich it is currently operating, without further verifying whether theballoon-state profile is associated with the requesting balloon'sgeographic area.

In some implementations, however, a balloon 206A to 206I that receives aprofile-update request may first determine whether it can indicate orprovide the balloon-state profile for the desired geographic area,before responding to the profile-update request. For example, if thereceiving balloon is operating according to the balloon-state profile ofa geographic area that is identified in profile-update request, then thereceiving balloon may respond by sending the requesting balloon itsballoon-state information and/or a balloon-state signal indicating orproviding some or all of the balloon-state profile according to whichthe receiving balloon is currently operating. On the other hand, if thereceiving balloon is not operating according to the balloon-stateprofile for the indicated geographic area and/or is not otherwise ableto indicate or provide some or all of the balloon-state profile for theindicated geographic area, then the receiving balloon may refrain fromresponding to the profile-update request with balloon-state information.Further, the receiving balloon may or may not send the requestingballoon a message indicating that it does not have balloon-stateinformation for the indicated geographic area.

In some embodiments, balloons may additionally or alternatively requestand/or receive some or all of a balloon-state profile from aground-based station. For example, a control system may maintain aprofile database indicating the settings for certain operationalparameters to be used by balloons while operating in a given geographicarea and/or other data that is associated with a given geographic area.Such a profile database may be searchable by geographic area, such thata balloon-state profile may be determined for a given geographic area.Accordingly, a control system may query the database to retrieve some orall of the balloon-state profile that is associated with a particulargeographic area. Further, there may be a single, central, database thatis searchable to determine particular balloon-state profiles, or anumber of separate databases that collectively provide the balloon-stateprofiles for all geographic areas in a balloon network.

In some embodiments, the control system may be central control system,which provides the balloon-state profiles for all geographic areas in aballoon network. In other embodiments, there may be a number of regionalcontrol systems, which may operate independently or may communicate witha central control system that coordinates and/or controls certainfunctions of the regional systems, such as is illustrated in FIG. 2.

More specifically, in the configuration illustrated in FIG. 2, regionalcontrol systems 202A to 202C may provide at least a portion of therespective balloon-state profile for each of geographic areas 220 to240. Accordingly, a balloon may update its balloon-state profileaccording to the balloon-state profile for a given geographic area 220to 240 by communicating with the regional control system 202A to 202Cthat is associated with the given geographic area.

Further, to update its state according to its current geographic area, aballoon may communicate directly with a regional control system 202A to202C, or may communicate indirectly with a regional control system viaother balloons and/or other ground-based stations. For example, in theillustrated state of balloon network 204, if balloon 206A determinesthat it should update its state with the balloon-state profile forgeographic area 220, then balloon 206A may send a profile-update requestto regional control system 202A. However, if balloon 206C determinesthat it should update its state with the balloon-state profile forgeographic area 220, then balloon 206C may send a profile-update requestto regional control system 202A indirectly; e.g., via balloon 206A orvia balloon 206B and 206A.

In some embodiments, a control system or systems may detect when aballoon 206A to 206I should update its state, and responsively notifythe balloon. Therefore, in such an embodiment, the balloon may not needto send a profile-update request in order to update its state. Forexample, a control system, such as one of regional control systems 202Ato 202C, may determine that a balloon is at a location that isassociated with a first geographic area of the balloon network, and thatthe balloon is operating according to a balloon-state profile for adifferent geographic area and/or that the balloon-state profile for thefirst geographic area has been updated since it was last provided to theballoon. In response, the control system may send the balloon a messageindicating that the balloon should update its state according to thecurrent balloon-state profile for the first geographic area.

Note that to facilitate a control system detecting when a balloon shouldupdate is state according to a different balloon-state profile, a givenballoon 206A to 206I may periodically send location update messages toone or more ground-based control systems, which indicate the balloon'slocation. As such, when a control system determines that a balloon hasmoved to a location associated with a new geographic area, the controlsystem may responsively send a balloon-state signal to the balloon,which indicates and/or provides some or all of the balloon-state profilefor the new geographic area. Further, the control system may initiate atransmission to the balloon of the user-data corresponding to thegeographic area.

E. Exemplary Balloon Configuration

Various types of balloon systems may be incorporated in an exemplaryballoon network. As noted above, an exemplary embodiment may utilizehigh-altitude balloons, which typically operate in an altitude rangebetween 18 km and 22 km. FIG. 3 shows a high-altitude balloon 300,according to an exemplary embodiment. As shown, the balloon 300 includesan envelope 302, a skirt 304, a payload 306, and a cut-down system 308that is attached between the balloon 302 and payload 304.

The envelope 302 and skirt 304 may take various forms, which may becurrently well-known or yet to be developed. For instance, the envelope302 and/or skirt 304 may be made of metalized Mylar or BoPet.Alternatively or additionally, some or all of the envelope 302 and/orskirt 304 may be constructed from a highly-flexible latex material or arubber material such as chloroprene. Other materials are also possible.Further, the shape and size of the envelope 302 and skirt 304 may varydepending upon the particular implementation. Additionally, the envelope302 may be filled with various different types of gases, such as heliumand/or hydrogen. Other types of gases are possible as well.

The payload 306 of balloon 300 may include a processor 312 and on-boarddata storage, such as memory 314. The memory 314 may take the form of orinclude a non-transitory computer-readable medium. The non-transitorycomputer-readable medium may have instructions stored thereon, which canbe accessed and executed by the processor 312 in order to carry out theballoon functions described herein.

The payload 306 of balloon 300 may also include various other types ofequipment and systems to provide a number of different functions. Forexample, payload 306 may include optical communication system 316, whichmay transmit optical signals via an ultra-bright LED system 320, andwhich may receive optical signals via an optical-communication receiver(e.g., a photo-diode receiver system). Further, payload 306 may includean RF communication system 318, which may transmit and/or receive RFcommunications via an antenna system 324.

The payload 306 may also include a power supply 326 to supply power tothe various components of balloon 300. The power supply 326 may includeor take the form of a rechargeable battery. In other embodiments, thepower supply 326 may additionally or alternatively represent other meansknown in the art for producing power. In addition, the balloon 300 mayinclude a solar power generation system 327. The solar power generationsystem 327 may include solar panels and could be used to generate powerthat charges and/or is distributed by the power supply 326.

Further, payload 306 may include various types of other systems andsensors 328. For example, payload 306 may include one or more videoand/or still cameras, a GPS system, various motion sensors (e.g.,accelerometers, gyroscopes, and/or compasses), and/or various sensorsfor capturing environmental data. Further, some or all of the componentswithin payload 306 may be implemented in a radiosonde, which may beoperable to measure, e.g., pressure, altitude, geographical position(latitude and longitude), temperature, relative humidity, and/or windspeed and/or direction, among other information.

As noted, balloon 306 includes an ultra-bright LED system 320 forfree-space optical communication with other balloons. As such, opticalcommunication system 316 may be configured to transmit a free-spaceoptical signal by modulating the ultra-bright LED system 320. Theoptical communication system 316 may be implemented with mechanicalsystems and/or with hardware, firmware, and/or software. Generally, themanner in which an optical communication system is implemented may vary,depending upon the particular application.

In a further aspect, balloon 300 may be configured for altitude control.For instance, balloon 300 may include a variable buoyancy system, whichis configured to change the altitude of the balloon 300 by adjusting thevolume and/or density of the gas in the balloon 300. A variable buoyancysystem may take various forms, and may generally be any system that canchange the volume and/or density of gas in envelope 302.

In an exemplary embodiment, a variable buoyancy system may include abladder 310 that is located inside of envelope 302. The bladder 310could be an elastic chamber configured to hold liquid and/or gas.Alternatively, the bladder 310 need not be inside the envelope 302. Forinstance, the bladder 310 could be a rigid bladder that could bepressurized well beyond neutral pressure. The buoyancy of the balloon300 may therefore be adjusted by changing the density and/or volume ofthe gas in bladder 310. To change the density in bladder 310, balloon300 may be configured with systems and/or mechanisms for heating and/orcooling the gas in bladder 310. Further, to change the volume, balloon300 may include pumps or other features for adding gas to and/orremoving gas from bladder 310. Additionally or alternatively, to changethe volume of bladder 310, balloon 300 may include release valves orother features that are controllable to allow gas to escape from bladder310. Multiple bladders 310 could be implemented within the scope of thisdisclosure. For instance, multiple bladders could be used to improveballoon stability.

In an example embodiment, the envelope 302 could be filled with helium,hydrogen or other lighter-than-air material. The envelope 302 could thushave an associated upward buoyancy force. In such an embodiment, air inthe bladder 310 could be considered a ballast tank that may have anassociated downward ballast force. In another example embodiment, theamount of air in the bladder 310 could be changed by pumping air (e.g.,with an air compressor) into and out of the bladder 310. By adjustingthe amount of air in the bladder 310, the ballast force may becontrolled. In some embodiments, the ballast force may be used, in part,to counteract the buoyancy force and/or to provide altitude stability.

In other embodiments, the envelope 302 could be substantially rigid andinclude an enclosed volume. Air could be evacuated from envelope 302while the enclosed volume is substantially maintained. In other words,at least a partial vacuum could be created and maintained within theenclosed volume. Thus, the envelope 302 and the enclosed volume couldbecome lighter than air and provide a buoyancy force. In yet otherembodiments, air or another material could be controllably introducedinto the partial vacuum of the enclosed volume in an effort to adjustthe overall buoyancy force and/or to provide altitude control.

In another embodiment, a portion of the envelope 302 could be a firstcolor (e.g., black) and/or a first material from the rest of envelope302, which may have a second color (e.g., white) and/or a secondmaterial. For instance, the first color and/or first material could beconfigured to absorb a relatively larger amount of solar energy than thesecond color and/or second material. Thus, rotating the balloon suchthat the first material is facing the sun may act to heat the envelope302 as well as the gas inside the envelope 302. In this way, thebuoyancy force of the envelope 302 may increase. By rotating the balloonsuch that the second material is facing the sun, the temperature of gasinside the envelope 302 may decrease. Accordingly, the buoyancy forcemay decrease. In this manner, the buoyancy force of the balloon could beadjusted by changing the temperature/volume of gas inside the envelope302 using solar energy. In such embodiments, it is possible that abladder 310 may not be a necessary element of balloon 300. Thus, variouscontemplated embodiments, altitude control of balloon 300 could beachieved, at least in part, by adjusting the rotation of the balloonwith respect to the sun.

Further, a balloon 306 may include a navigation system (not shown). Thenavigation system may implement station-keeping functions to maintainposition within and/or move to a position in accordance with a desiredtopology. In particular, the navigation system may use altitudinal winddata to determine altitudinal adjustments that result in the windcarrying the balloon in a desired direction and/or to a desiredlocation. The altitude-control system may then make adjustments thedensity of the balloon chamber in order to effectuate the determinedaltitudinal adjustments and cause the balloon to move laterally to thedesired direction and/or to the desired location.

Alternatively, the altitudinal adjustments may be computed by aground-based control system and communicated to the high-altitudeballoon. As another alternative, the altitudinal adjustments may becomputed by a ground-based or satellite-based control system andcommunicated to the high-altitude balloon. Furthermore, in someembodiments, specific balloons in a heterogeneous balloon network may beconfigured to compute altitudinal adjustments for other balloons andtransmit the adjustment commands to those other balloons.

As shown, the balloon 300 also includes a cut-down system 308. Thecut-down system 308 may be activated to separate the payload 306 fromthe rest of balloon 300. This functionality may be utilized anytime thepayload needs to be accessed on the ground, such as when it is time toremove balloon 300 from a balloon network, when maintenance is due onsystems within payload 306, and/or when power supply 326 needs to berecharged or replaced.

In an exemplary embodiment, the cut-down system 308 may include aconnector, such as a balloon cord, connecting the payload 306 to theenvelope 302 and a means for severing the connector (e.g., a shearingmechanism or an explosive bolt). In an example embodiment, the ballooncord, which may be nylon, is wrapped with a nichrome wire. A currentcould be passed through the nichrome wire to heat it and melt the cord,cutting the payload 306 away from the envelope 302. Other types ofcut-down systems and/or variations on the illustrated cut-down system308 are possible as well.

In an alternative arrangement, a balloon may not include a cut-downsystem. In such an arrangement, the navigation system may be operable tonavigate the balloon to a landing location, in the event the balloonneeds to be removed from the network and/or accessed on the ground.Further, it is possible that a balloon may be self-sustaining, such thatit theoretically does not need to be accessed on the ground. In yetother embodiments, balloons may be serviced in-flight by specificservice balloons or another type of service aerostat or serviceaircraft.

III. Balloon Network with Optical and RF Links Between Balloons

In some embodiments, a high-altitude-balloon network may includesuper-node balloons, which communicate with one another via opticallinks, as well as sub-node balloons, which communicate with super-nodeballoons via RF links. FIG. 4 is a simplified block diagram illustratinga balloon network that includes super-nodes and sub-nodes, according toan exemplary embodiment. More specifically, FIG. 4 illustrates a portionof a balloon network 400 that includes super-node balloons 410A to 410C(which may also be referred to as “super-nodes”) and sub-node balloons420A to 420Q (which may also be referred to as “sub-nodes”).

Each super-node balloon 410A to 410C may include a free-space opticalcommunication system that is operable for packet-data communication withother super-node balloons. As such, super-nodes may communicate with oneanother over optical links. For example, in the illustrated embodiment,super-node 410A and super-node 401B may communicate with one anotherover optical link 402, and super-node 410A and super-node 401C maycommunicate with one another over optical link 404.

Each of the sub-node balloons 420A to 420Q may include a radio-frequency(RF) communication system that is operable for packet-data communicationover one or more RF air interfaces. Accordingly, some or all of thesuper-node balloons 410A to 410C may include an RF communication systemthat is operable to route packet data to one or more nearby sub-nodeballoons 420A to 420Q. When a sub-node 420A receives data from asuper-node 410A via an RF link, the sub-node 420A may in turn use its RFcommunication system to transmit the received data to a ground-basedstation 430A to 430L via an RF link.

In some embodiments, all sub-node balloons may be configured toestablish RF links with ground-based stations. For example, allsub-nodes may be configured similarly to sub-node 420A, which isoperable to relay communications between super-node 410A and aground-based station 430A via respective RF links.

In other embodiments, some or all sub-nodes may also be configured toestablish RF links with other sub-nodes. For instance, in theillustrated embodiment, sub-node balloon 420F is operable to relaycommunications between super-node 410C and sub-node balloon 420E. Insuch an embodiment, two or more sub-nodes may provide a multi-hop pathbetween a super-node balloon and a ground-based station, such as themulti-hop path provided between super-node 410C and a ground-basedstation 430E by sub-node balloons 420E and 420F.

Note that an RF link may be a directional link between a given entityand one or more other entities, or may be part of an omni-directionalbroadcast. In the case of an RF broadcast, it is possible that one ormore “links” may be provided via a single broadcast. For example,super-node balloon 410A may establish a separate RF link with each ofsub-node balloons 420A, 420B, and 420C. However, in otherimplementations, super-node balloon 410A may broadcast a single RFsignal that can be received by sub-node balloons 420A, 420B, and 420C.In such an implementation, the single RF broadcast may effectivelyprovide all of the RF links between super-node balloon 410A and sub-nodeballoons 420A, 420B, and 420C. Other examples are also possible.

Generally, the free-space optical links between super-node balloons havemore bandwidth capacity than the RF links between super-node balloonsand sub-node balloons. Further, free-space optical communication may bereceived at a much greater distance than RF communications. As such, thesuper-node balloons 410A to 410C may function as the backbone of theballoon network 400, while the sub-nodes 420A to 420Q may providesub-networks providing access to the balloon network and/or connectingthe balloon network to other networks.

As noted above, the super-nodes 410A to 410C may be configured for bothlonger-range optical communication with other super-nodes andshorter-range RF communications with nearby sub-nodes 420. For example,super-nodes 410A to 410C may use high-power or ultra-bright LEDs totransmit optical signals over optical links 402, 404, which may extendfor as much as 100 miles, or possibly more. Configured as such, thesuper-nodes 410A to 410C may be capable of optical communications atdata rates of 10 to 50 Gbit/sec.

A larger number of high-altitude balloons may then be configured assub-nodes, which may communicate with ground-based Internet nodes atdata rates on the order of approximately 10 Mbit/sec. For instance, inthe illustrated implementation, the sub-nodes 420A to 420Q may beconfigured to connect the super-nodes 410A to 410C to other networksand/or directly to client devices. Note that the data rates and linkdistances described in the above example and elsewhere herein areprovided for illustrative purposes and should not be consideredlimiting; other data rates and link distances are possible.

In a further aspect, some or all of the super-node balloons may beconfigured as downlink balloons. Additionally or alternatively, some orall of sub-nodes 420A to 420Q may be configured as downlink balloons.Further, it is possible that a hierarchical balloon network such as thatshown in FIG. 4 may be implemented without any downlink balloons.

Further, in some embodiments, the super-node balloons, such assuper-nodes 410A to 410C, may function as a core network (i.e., abackbone network), while the sub-node balloons 420A to 420Q may functionas one or more access networks to the core network of super-nodes. Insuch an embodiment, some or all of the sub-nodes 420A to 420Q may alsofunction as gateways to the balloon network 400. Note also that in someembodiments, some or all of the ground-based stations 430A to 430L mayadditionally or alternatively function as gateways to balloon network400.

In another aspect, it should be understood that the network topology ofthe hierarchical balloon network shown in FIG. 4 is but one of manypossible network topologies. Further, the network topology of anexemplary balloon network may vary dynamically as super-node and/orsub-node balloons move relative to the ground and/or relative to oneanother. Further, as with the balloon networks illustrated in FIGS. 1and 2, a desired topology may be specified for a hierarchical balloonnetwork may change dynamically over time as service needs and/or goalsof the network change.

Location-specific balloon-state profiles may also be implemented in aheterogeneous balloon network, such as balloon network 400. For example,as shown in FIG. 4, geographic areas 470, 480, and 490 may be definedwithin the coverage area of balloon network 400.

In an embodiment where super-node balloons 410A to 410C serve as a corenetwork, and sub-node balloons 420A to 420Q provide an access network oraccess networks, location-specific balloon-state profiles may only beimplemented by the sub-node balloons 420A to 420Q. Alternatively, bothsuper-node balloons 410A to 410C and sub-node balloons 420A to 420Q canimplement location-specific balloon-state profiles.

Further, in some embodiments, a super-node balloon 410A to 410C mayfacilitate implementation of location-specific balloon-state profiles bysome or all of sub-node balloons 420A to 420Q. For example, eachsuper-node balloon 410A to 410C could store a balloon-state profile fora certain geographic area 470 to 490, respectively. As such, a sub-nodeballoon 420A to 420Q could query a nearby super-node balloon for theballoon-state profile that is associated with the geographic area inwhich it located or anticipates that it will soon be located.Alternatively, a super-node balloon 410A to 410C may function as acontrol system, in a similar manner as described above in reference toFIG. 2. Other implementations of location-specific balloon-stateprofiles in heterogeneous balloon networks are also possible.

V. Examples of Methods

A. Example Balloon-Implemented Methods for a Updating Balloon StateAccording to Location-Specific Balloon-State Profiles

FIG. 5A is a simplified flow chart illustrating a method 500, accordingto an exemplary embodiment. Method 500 may be implemented by a balloonin a balloon network to maintain and/or update its state as it moves todifferent geographic areas in a balloon network, according to thelocation-specific balloon-state profiles for the different GAs, andpossibly for other purposes as well or instead.

More specifically, method 500 involves a balloon, which is at a locationassociated with the first geographic area in a balloon network,determining that its state (also referred to herein as the“balloon-state” of the balloon) should be updated in accordance with aballoon-state profile for the first geographic area, as shown by block502. Responsive to determining that its balloon-state should be updated,the balloon may determine the balloon-state profile for the firstgeographic area, which may specify one or more state parameters forballoons operating in the first geographic area, as shown by block 504.The balloon may then operate according to the balloon-state profile forthe first geographic area, as shown by block 506.

In an exemplary method 700, the state parameters specified by aballoon-state profile may include various operational parameters for aballoon. For instance, a service protocol for a given geographic areamay specify: (a) a communication protocol or protocols to be used forcommunications with ground-based stations and/or other balloons in thearea, (b) parameters for routing between balloons and ground-basedstations in area, (c) transmission power requirements (e.g., minimumand/or maximum transmission power), (d) error correction coding, (e) adesired topology for the portion of the balloon network serving thearea, (f) identifying information and/or other information relating toground-based stations or other fixed systems in the area, which theballoon can connect to (e.g., to connect with other networks), (g) powermanagement of balloon while in the area, (h) parameters affecting thehorizontal and/or altitudinal movement of the balloon (e.g., limits onspeed, a maximum altitude, and/or a minimum altitude, etc.), and/or (i)parameters required in order to fall within a desired regulatory classset out by the government of the country in which the area is located,or to otherwise comply with legal requirements or regulations in thegeographic area, among others.

In some embodiments, the balloon-state profile for a given geographicarea may include state parameters that provide or identify data thatshould be acquired, stored, and/or provided by the balloon whileoperating in the geographic area. Such data may include, for example,commonly-accessed web pages in certain language, program instructionsfor language-specific functionality that is required or used to operateaccording to the operational parameters, and/or other types of data thatmay be useful in some locations, but not in others.

In some embodiments, the balloon-state profile for a given geographicarea may include state parameters that indicate certain modes ofoperation for a geographic area. The state parameters that define a modeof operation for a given geographic area may be highly adaptable to helpoptimize service for a given geographic area.

For example, consider the scenario where a geographic area with highbandwidth utilization (e.g., a high-usage area) is adjacent togeographic area with significantly lower bandwidth utilization (e.g., alow-usage area). Further, in the geographic areas, the balloon networkmay provide service to some high-priority subscribers (e.g., subscriberswho have paid for premium service) and some low-priority subscribers(e.g., subscribers who have not paid for the premium service). A stateparameter may specify whether a first or second mode of operation shouldbe utilized in a given geographic area, where implementing the firstmode of operation specifies a lower threshold bandwidth utilization forrestricting the amount of bandwidth allocated to a low-prioritysubscriber than is specified by the second mode of operation. Thus, theballoon-state profile for the high-usage area may indicate the firstmode of operation, while the balloon-state profile for the low-usagearea may indicate the second mode of operation. Thus, a balloon thatleaves a high-usage area and enters an adjacent low-usage area mayincrease the threshold bandwidth utilization at which it restricts theamount of bandwidth that can be allocated to a low-priority subscriber.As a result, a balloon may accept a greater number of bandwidth requestsfrom low-priority subscribers in the low-usage area, than it did whileoperating according to the balloon-state profile for the high-usagearea. Other examples are also possible.

i. Determining that Balloon-State Information should be Updated

At block 502 of an exemplary method 500, a balloon may use varioustechniques to determine that it should update its state in accordancewith the balloon-state profile for a certain geographic area.

For example, a balloon may detect when it moves from a location that isnot associated with a first geographic area (e.g., that is outside thefirst geographic area), to a location within the first geographic area.When movement into the first geographic area is detected, the balloonwill likely be operating in accordance with the balloon-state profilefor the geographic area in which it was previously located. Accordingly,when the balloon detects that it has moved into a new geographic area,the balloon may respond by proceeding to send a profile-update requestat block 504.

In some implementations, block 502 may involve the balloon detecting amovement of the balloon into a border area of the first geographic area,from a location that is not associated with the first geographic area(e.g., from a location that is outside the border area and in anothergeographic area), such as is described above in reference to FIG. 2.When the balloon moves into a border area of a geographic area, this maybe interpreted to mean that the balloon is moving towards the geographicarea. Accordingly, a balloon may respond to movement into a border areaby sending a profile-update request at block 504.

Note that when a balloon moves into a border area, a balloon may alsocheck its previous, current, and/or planned direction of movement toverify that it is heading towards a different geographic area (e.g.,from another geographic area into the first GA). Further, based on theprevious, current, and/or planned direction of movement, the balloon maydetermine the probability that it will move into the differentgeographic area. As such, when the balloon is located in a border area,the balloon may condition the transmission of a profile-update request,at block 504, upon a determination that the probability of moving intothe first geographic area is greater than a threshold probability.

In a further aspect, to determine when to update its state, a balloonmay run a background process to monitor its location and detect when itmoves into a new geographic area and/or when it moves into a borderarea, and should therefore update, or prepare to update, its stateaccording to the balloon-state profile of a different geographic area.

ii. Determining the Balloon-State Profile for a Geographic Area

At block 504 of method 500, a balloon may use various techniques todetermine the balloon-state profile for a given geographic area.

In some embodiments, the balloon may acquire some or all of theinformation making up a balloon-state profile from nearby balloons thatare operating in the balloon network. In such an embodiment, block 504may involve the balloon sending a profile-update request to one or moreother balloons. The balloon may then receive at least a portion of therequested balloon-state profile for the first geographic area from oneor more balloons that received the profile-update request.

In some embodiments, the balloon may additionally or alternatively senda profile-update request to at least one ground-based station that isassociated with the geographic area for which the balloon-state profileis being requested. As such, a balloon may acquire some or all of theinformation making up a balloon-state profile from the ground-basedstation or stations that are located in or otherwise associated with thegeographic area.

In some cases, the balloon may receive the entire balloon-state profilefor a geographic area from a single nearby balloon, which responds tothe profile-update request. In other cases, a balloon may receivedifferent portions of the balloon-state profile from a number ofdifferent balloons. In yet other cases, a balloon may receive a portionor portions of the balloon-state profile from one or more nearbyballoons, and receive another portion or portions from one or moreground-based stations.

In some embodiments, some or all balloons that operate in a balloonnetwork may be configured to broadcast a balloon-state signal via adesignated communications channel, which indicates at least a portion ofthe balloon-state profile for a geographic area with which thebroadcasting balloon is associated (e.g., the geographic area in whichthe balloon is currently located or a geographic area that the balloonwas recently located in). In such an embodiment, block 504 may involvethe balloon that seeks to determine the balloon-state profile for thefirst geographic area, searching the designated communication channelfor a balloon-state signal that indicates at least a portion of theballoon-state profile for the first geographic area.

FIG. 5B is a flow chart illustrating a method 550, which is acontinuation of the method 500 shown in FIG. 5A, according to anexemplary embodiment. Method 550 may be implemented, for example, afterthe balloon has updated its state according to the balloon-state profilefor the first geographic area, when the balloon moves from the firstgeographic area to a second geographic area.

More specifically, method 550 involves the balloon determining that theballoon is at a location associated with a second geographic area of theballoon network (e.g., a location within the second geographic area orwithin a border area of the second GA), as shown by block 552. Theballoon may then determine that it should update its state in accordancewith the balloon-state profile for the second geographic area, as shownby block 554. Then, in response to determining that it should update itsstate, the balloon may determine the balloon-state profile for thesecond geographic area, which includes one or more state parameters forballoons operating in the second geographic area, as shown by block 556.The balloon may then operate according to the balloon-state profile forthe second geographic area, as shown by block 558.

Further, a given balloon in a balloon network may repeat method 500 orportions thereof (e.g., such as by carrying out method 550) whenever itdetects it has moved or is about to move into a different geographicarea. By doing so, a given balloon may adjust its state according to theballoon-state profile in whatever geographic area the balloon is locatedin and/or expects to be located in.

In a further aspect, a number of balloons may implement method 500and/or method 550, as the balloons move between geographic areas in aballoon network, the fact that balloons are moving into and out of ageographic area may be substantially transparent to an end user in thegeographic area. In particular, when a first balloon moves out of ageographic area, end users that are communicating via the first balloonmay be handed off to a second balloon that is operating in thegeographic area. The second balloon can also implement method 500 and/ormethod 550, and thus, the second balloon may still be operatingaccording to the balloon-state profile for the geographic area. Further,as other balloons move into the geographic area, the other balloons mayimplement method 500 and/or method 550, and thus may update theirrespective states so as to operate according to balloon-state profilefor the geographic area. This functionality of the balloons maycollectively help to provide continuity in service and network operationin the geographic area, even though the balloon or balloons that operatein the geographic area change over time.

In a further aspect, there may be scenarios where it undesirable for aballoon to move out of a geographic area, unless at least one otherballoon takes its place in the geographic area. Accordingly, a balloonmay be further operable to determine whether a replacement balloon isneeded and/or taking steps to find a replacement plan. For example, aballoon may determine

As a specific example, consider an embodiment where block 502 involvesthe balloon determining that it is in a border area, and likely to moveinto a different geographic area. In such an embodiment, the balloon mayresponsively determine how many other balloons are located in thegeographic area (and presumably configured according to theballoon-state profile for the GA). To do so, the balloon may broadcast amessage requesting that nearby balloons indicate whether they arelocated in and/or operating according to the balloon-state profile for,the geographic area that the balloon is about to or expects to move outof. A balloon could also send a message to a ground-based stationrequesting information indicative of which and/or how many otherballoons are currently in a geographic area and/or operating accordingto the balloon-state profile for the geographic area. Additionally oralternatively, the identity and/or balloon-state of nearby balloons mayalready be stored at the balloon. For instance, balloons may beconfigured to maintain and update a database of nearby balloons by e.g.,communicating location and/or balloon-state information to one anotherand/or receiving such information from ground-based stations.

Once a balloon identifies other balloons in the geographic area that itis about to move out of, the balloon may determine whether anotherballoon should take its place in the geographic area. For example, adensity requirement may be defined for a geographic area, which mayindicate, for example, a minimum and/or maximum number of balloons thatshould provide service in the geographic area at a given point in time.As such, the balloon may compare the current number of other balloonsoperating in the geographic area to a minimum number for the geographicarea and, if the current number is less than the minimum number, maytake actions to find a replacement. For example, the balloon may send amessage to nearby balloons and/or a ground-based station that isassociated with the geographic area, which indicates: (a) that theballoon has moved, or is about to or expects to move, out of thegeographic area, and/or (b) that another balloon should move into thegeographic area and update its state according to the balloon-stateprofile for the geographic area. Other examples are also possible.

B. Method for Providing a Balloon-State Profile to Other Balloons

FIG. 6 is a simplified flow chart illustrating a method 600, accordingto an exemplary embodiment. Method 600 may be implemented by a balloonin a balloon network to, e.g., hand off some or all of a balloon-stateprofile for a geographic area, to another balloon that has entered or isabout to enter the geographic area.

More specifically, method 600 involves a balloon determining aballoon-state profile for a first geographic area, which includes one ormore state parameters for balloons operating in the first geographicarea, as shown by block 602. In an example embodiment, the firstgeographic area may be the geographic area in which the balloon iscurrently located. The balloon may then generate a balloon-state signal,which indicates at least a portion of the balloon-state profile for thefirst geographic area, as shown by block 604. The balloon can thentransmit the balloon-state signal via a communication channel that isaccessible to other balloons in the balloon network, as shown by block606.

In some embodiments of method 600, the balloon may broadcast theballoon-state signal via a communication channel, such that theballoon-state signal is available to any balloon that is monitoring thecommunication channel. For example, a network-coordination channel maybe defined over an RF air-interface. As such, the balloon-state signalmay be an RF signal, which the balloon broadcasts on thenetwork-coordination channel. In such an example, other balloons mayacquire the balloon-state signal by monitoring and/or searching thenetwork-coordination channel for balloon-state signals. Other types ofballoon-state signals are also possible.

In other embodiments, the balloon may send the balloon-state signalspecifically to a second balloon or to multiple other balloons. In suchan embodiment, a first balloon may initially determine that a secondballoon should be updated with the balloon-state profile for the firstgeographic area. This may simply involve the first balloon receiving aprofile-update request from the second balloon. Alternatively, the firstballoon may send a message requesting that the second balloon indicatethe balloon-state profile that the second balloon is currentlyimplementing, and determine that the second balloon's balloon-stateprofile is not current (e.g., is associated with a different geographicarea than the second balloon is currently operating in). In either case,when the first balloon determines that the state of the second balloonshould be updated, then the first balloon may responsively send aballoon-state signal (which may also be referred to as a “balloon-statemessage”) to the second balloon. In such an embodiment, thecommunication channel that is utilized to send the balloon-state signalto the second balloon may be defined on an RF air interface, on afree-space optical link, or on another wireless link or wirelessair-interface between the two balloons.

IV. Conclusion

The particular arrangements shown in the Figures should not be viewed aslimiting. It should be understood that other embodiments may includemore or less of each element shown in a given Figure. Further, some ofthe illustrated elements may be combined or omitted. Yet further, anexemplary embodiment may include elements that are not illustrated inthe Figures.

Additionally, while various aspects and embodiments have been disclosedherein, other aspects and embodiments will be apparent to those skilledin the art. The various aspects and embodiments disclosed herein are forpurposes of illustration and are not intended to be limiting, with thetrue scope and spirit being indicated by the following claims. Otherembodiments may be utilized, and other changes may be made, withoutdeparting from the spirit or scope of the subject matter presentedherein. It will be readily understood that the aspects of the presentdisclosure, as generally described herein, and illustrated in thefigures, can be arranged, substituted, combined, separated, and designedin a wide variety of different configurations, all of which arecontemplated herein.

We claim:
 1. A computer-implemented method comprising: while an aerialvehicle is at a location associated with a second geographic area,operating the aerial vehicle according to a second vehicle-stateprofile, wherein the second vehicle-state profile specifies one or moreoperational parameters for use by aerial vehicles from an aerial networkwhile located in the second geographic area; subsequently determining,by the aerial vehicle, that the aerial vehicle has moved to a locationassociated with a first geographic area; and in response to determiningthat the aerial vehicle has moved to a location associated with thefirst geographic area: determining a first vehicle-state profile for thefirst geographic area, wherein the first vehicle-state profile specifiesone or more operational parameters for use by aerial vehicles from theaerial network while located in the first geographic area; and causingthe aerial vehicle to switch from operation according to the secondvehicle-state profile to operate according to the first vehicle-stateprofile.
 2. The method of claim 1, wherein determining that the aerialvehicle has moved to a location associated with the first geographicarea comprises: determining that the aerial vehicle has moved to alocation within the first geographic area.
 3. The method of claim 1,wherein determining that the aerial vehicle has moved to a locationassociated with the first geographic area comprises: determining thatthe aerial vehicle has moved into a border area that is adjacent to thefirst geographic area.
 4. The method of claim 3, wherein the border areais between the first geographic area and the second geographic area. 5.The method of claim 3, wherein the border area is an edge portion of thesecond geographic area that is adjacent to the first geographic area. 6.The method of claim 5, wherein sending the profile-update requestcomprises sending the profile-update request to one or more other aerialvehicles in the aerial network, and wherein at least a portion of thefirst vehicle-state profile is received from one or more of the otheraerial vehicles.
 7. The method of claim 5, wherein sending theprofile-update request comprises: sending the profile-update request toa ground-based station that is associated with the first geographicarea, wherein at least a portion of the first vehicle-state profile isreceived from the ground-based station.
 8. The method of claim 3,further comprising: determining a direction in which the aerial vehicleis travelling; and determining whether or not the direction in which theaerial vehicle is travelling is towards the first geographic area;wherein the responsive determination of the first vehicle-state profileand switch from operation according to the second vehicle-state profileto operation according to the first vehicle-state profile, areconditioned upon a determination that the direction in which the aerialvehicle is travelling is towards the first geographic area.
 9. Themethod of claim 1, wherein determining the first vehicle-state profilecomprises: sending a profile-update request; and receiving, as aresponse to the profile-update request, at least a portion of the firstvehicle-state profile.
 10. The method of claim 1, wherein determiningthe first vehicle-state profile comprises: searching a communicationchannel for a vehicle-state signal; and receiving the vehicle-statesignal via the communication channel, wherein the vehicle-state signalindicates at least a portion of the first vehicle-state profile.
 11. Themethod of claim 1, wherein the one or more operational parametersindicated by the first vehicle-state profile comprise one or more of:(a) at least one parameter indicating a communication protocol orprotocols to be used in the first geographic area, (b) at least oneparameter providing routing information for the first geographic area,(c) at least one parameter relating to transmission power for aerialvehicles operating in the first geographic area, (d) at least oneparameter indicative of error correction coding that should beimplemented by an aerial vehicle in the first geographic area, (e) atleast one parameter indicative of a desired topology for the aerialnetwork in the first geographic area, (f) at least one parameter thatprovides information related to ground-based stations or other fixedsystems in the first geographic area, (g) at least one parameterindicative of power management that should be implemented by an aerialvehicle in the first geographic area, (h) at least one parameteraffecting the horizontal and/or altitudinal movement of the aerialvehicle, and/or (i) at least one parameter providing information forcomplying with a legal requirement for the first geographic area. 12.The method of claim 1, further comprising: subsequently, after causingthe aerial vehicle to operate according to the first vehicle-stateprofile, determining that the aerial vehicle at a location associatedwith the second geographic area of the aerial network; in response tothe subsequent determination that the aerial vehicle is at a locationassociated with the second geographic area, causing the aerial vehicleto again operate according to the second vehicle-state profile.
 13. Acomputer-implemented method comprising: while an aerial vehicle isoperating in an aerial network and is at a location associated with asecond geographic area, transmitting a second vehicle-state signal thatis accessible to one or more other aerial vehicles in the aerialnetwork, wherein the second vehicle-state signal provides at least aportion of a second vehicle-state profile for the second geographicarea, and wherein the second vehicle state profile comprises one or moreoperational parameters for use by aerial vehicles from an aerial networkwhile located in the second geographic area; and subsequentlydetermining that the aerial vehicle is at a location associated with afirst geographic area in the aerial network, and responsively:transmitting a first vehicle-state signal that is accessible to one ormore other aerial vehicles in the aerial network, wherein the firstvehicle-state signal provides at least a portion of a firstvehicle-state profile for the first geographic area, and wherein thefirst vehicle-state profile comprises one or more operational parametersfor use by aerial vehicles from the aerial network while located in thefirst geographic area.
 14. The method of claim 13: wherein transmittingthe first vehicle-state signal comprises broadcasting the firstvehicle-state signal over a first communication channel, such that thefirst vehicle-state signal is available to any aerial vehicle in theaerial network that is monitoring the first communication channel; andwherein transmitting the second vehicle-state signal comprisesbroadcasting the second vehicle-state signal over a second communicationchannel, such that the second vehicle-state signal is available to anyaerial vehicle in the aerial network that is monitoring the secondcommunication channel.
 15. The method of claim 14, wherein the firstcommunication channel is defined on a first RF air-interface, andwherein the second communication channel is defined on a second RFair-interface.
 16. The method of claim 14, wherein the aerial vehicle isa first aerial vehicle, and wherein the first communication channel isdefined on a free-space optical link between the first aerial vehicleand a second aerial vehicle.
 17. The method of claim 13, wherein theaerial vehicle is a first aerial vehicle, the method further comprising:while the first aerial vehicle is at a location associated with thefirst geographic area, determining, at the first aerial vehicle, that asecond aerial vehicle should be updated with the vehicle-state profilefor the first geographic area; and responsively sending the firstvehicle-state signal from the first aerial vehicle to the second aerialvehicle.
 18. A non-transitory computer-readable medium having programinstructions stored thereon that are executable by at least oneprocessor, the program instructions comprising: instructions for, whilean aerial vehicle is operating in an aerial network and is at a locationassociated with a second geographic area, transmitting a secondvehicle-state signal that is accessible to one or more other aerialvehicles in the aerial network, wherein the second vehicle-state signalprovides at least a portion of a second vehicle-state profile for thesecond geographic area, and wherein the second vehicle state profilecomprises one or more operational parameters for use by aerial vehiclesfrom an aerial network while located in the second geographic area; andinstructions for subsequently determining that the aerial vehicle is ata location associated with a first geographic area in the aerialnetwork, and responsively: transmitting a first vehicle-state signalthat is accessible to one or more other aerial vehicles in the aerialnetwork, wherein the first vehicle-state signal provides at least aportion of a first vehicle-state profile for the first geographic area,and wherein the first vehicle-state profile comprises one or moreoperational parameters for use by aerial vehicles from the aerialnetwork while located in the first geographic area.
 19. Thenon-transitory computer-readable medium of claim 18, wherein theinstructions for transmitting the first vehicle-state signal compriseinstructions for broadcasting the first vehicle-state signal such thatthe vehicle-state signal is available to any aerial vehicle that ismonitoring a first communication channel.
 20. The non-transitorycomputer-readable medium of claim 18, wherein the aerial vehicle is afirst aerial vehicle, the method further comprising: instructions fordetermining, at the first aerial vehicle, that a second aerial vehicleshould be updated with the first vehicle-state profile for the firstgeographic area, and responsively sending the first vehicle-state signalto the second aerial vehicle.